1. Field of the Invention
The present invention relates a methods of and apparatus for composting a mixture of biological waste material and sludge.
More particularly, the present invention is useful, for example, for the treatment of biological waste and sludge by dewatering and composting to form fertilizer, and for the conversion of waste water into usable water or even into drinking water, and may be employed for the treatment of waste, in waste treatment plants, from municipal sewerage systems, industrial sewage treatment plants, and other sources of human and animal waste, for example slaughter houses, hospitals and other buildings, greenhouses and other agricultural installations. The present apparatus may be connected to or separate from sewers and is useful both in fixed installations and in mobile waste treatment apparatus.
2. Description of the Prior Art
Various types of apparatuses for the composting of waste materials are already known, which mostly are fed from the top, are ventilated from the sides and from below and are emptied at the bottom. These prior apparatuses employ a composting process which is very complicated and which results in many cold spots, and consequently mold fungus growth, and in addition they require a composting period of about three months.
In European Patent Application 85114214.1, in the name of Gunther Abel et al., there is disclosed a method of and apparatus for the treatment of biological waste and sludge which mitigate these disadvantages by making possible a trouble-free and intensive mixing of waste materials and also provide effective heat exchange.
In this prior method and apparatus, floating material and clarified sludge from sewage treatment plants and biological waste from domestic, industrial and other sources are treated, screenings, floating material and clarified sludge being separated, the biological waste being chopped up and the sludge being fed into the biological waste. More particularly, floating waste material is fed into a screening apparatus and passed into a mixing chamber, in which it is mixed with screenings, comminuted biological waste and recycled biological waste passing down through a chopping mechanism. The mixture is dewatered and compacted to about 50% solid content.
A first part of the compacted mass is fed to a mixing chamber to which clarified sludge is also supplied and is mixed with this sludge
The remainder of the compacted mass is fed into an upwardly inclined auger, which is adapted to heat the material by heat exchange. The material is also aerated and is thus composted over a period of 5-10 days. The compost is sieved and bagged.
The separated first part of the compacted mass, mixed with the clarified sludge, is fed to another auger, in which heat exchange is also effected.
The two augers are coaxial and insulated in order to conserve heat, and the apparatus is mobile for transfer between sewage treatment plants at different locations.
Activated sludge is also supplied to the mixing chamber from a settling tank and an inlet is also provided for the flow of fresh sludge into the mixing chamber.
This prior method and apparatus utilize two different types of bacteria, namely aerobic bacteria and anaerobic bacteria, in two endless paths of travel. Also, they enable the material being treated to be compacted only to about 50% of its original volume.